Monolithic integration of InGaAs/InP DFB lasers and InGaAs/InAlAs MQW optical modulators

The first successful monolithic integration of InGaAsP/InP distributed feedback (DFB) lasers and InGaAs/InAlAs multiple quantum well (MQW) optical modulators using LPE (liquid phase epitaxy)/MBE (modlecular beam epitaxy) hybrid growth reported. A 14% light output modulation is observed in this integrated device.     

Capturing of acidic macromolecules from biological samples using a temperature-responsive polymer modified with poly-l-lysine

We synthesized a temperature-responsive polymer, N-(isopropylacrylamide)-methacrylic acid copolymer, to which poly-l-lysine was introduced. The synthesized polymer as well as the parent polymer showed reversible soluble-insoluble changes in response to temperature changes across the lower critical solution temperature at 32 degree C in an aqueous solution. We found that the polymer efficiently captured acidic bio-macromolecules such as RNA, glycosaminoglycans and mucin-type glycoproteins in biological samples, and the captured molecules were recovered using aqueous NaCl solutions at high concentration. The target acidic molecules thus obtained will be employed for further studies such as structural analysis after brief desalting procedure. The proposed method does not require any chromatographic separations, but only needs a small volume of an aqueous salt solution for releasing captured molecules. Overall procedures are quite easy and simple, and are completed at least within 1 h. We show a few examples for capturing RNA and glycosaminoglycans from cultured cells using the polymer.     

Comparison of coupling characteristics for several spotsize-converter-integrated laser diodes in the 1.3-/spl mu/m-wavelength region

Four types of spotsize-converter-integrated laser diodes (SS-LDs) are numerically compared from the viewpoint of the coupling characteristics to the single-mode fiber in the 1.3-/spl mu/m-wavelength region. The comparison is based on the semivectorial three-dimensional (3-D) finite-difference (FD) beam propagation method (BPM). The SS-LDs investigated here are categorized into a group with vertical tapers and a group with a combination of a lateral taper and a thin-film core. The features of the SS-LDs are clarified.     

3-D semivectorical beam propagation analysis of a spotsize-converter-integrated laser diode in the 1.3-/spl mu/m-wavelength region

Spotsize converters (SSCs), consisting of a lateral taper, thin-film core, and ridge, have been accurately designed to develop spotsize-converted laser diodes (SS-LDs) in the 1.3-/spl mu/m-wavelength region based on the 3-D semivectorial finite-difference beam propagation method (FD-BPM) with nonequidistant discretization. The effects of the structural parameters on the sum of spot-conversion loss and coupling loss between the laser diode eigenmode and single-mode fiber (SMF) eigenmode are clarified. It is shown that a small loss of around 1.5 dB can be realized by introducing nonlinear tapers to these types of SSC's. The calculated results agree well with the measured results.     

X-ray analysis of supercooled water

X-ray diffraction patterns of supercooled water were obtained at -5 and -10°C. Pretreated X-ray film was used for the measurements. X-ray intensity was measured by counting the density of developed Ag grains under a microscope. The radial distribution functions were derived from the intensity curves.     

1.55 μm InGaAsP/InP laser buried in a high-resistivity epitaxiallayer on a semi-insulating InP substrate

A buried heterostructure (BH) 1.55 μm laser embedded in a high resistivity epitaxial layer on a semi-insulating substrate is described. This device has a planar surface and both a p- and an n-type electrode on the same side, facilitating integration of electronic devices. Its threshold current is typically 9 mA. Its small signal 3 dB modulation bandwidth was 14 GHz due to the reduction of device resistance and capacitance. No degradation was observed in an aging test at 50°C even after more than 3000 h     

Reliability and degradation behaviors of semi-insulating Fe-doped InP buried heterostructure lasers fabricated by movpe and dry etching technique

We clarified the degradation behavior of semi-insulating buried heterostructure lasers in which mesa structures were fabricated by RIE and then buried by MOVPE. The degradation rate and mode correlated with the quality of the BH interface. Based on the correlation, a condition for highly stable SIBH lasers was demonstrated and confirmed experimentally and statistically.     

GaxIn1-xAsyP1-y/InP injection laser partially loaded with first-order distributed Bragg reflector

GaInAsP/InP distributed Bragg reflector (DBR) lasers with a first-order grating were demonstrated experimentally for the first time at a wavelength of 1.3 μm. Single longitudinal mode oscillation was obtained at low temperature, and the temperature dependence of the lasing wavelength was 0.7-0.8 Å/deg. The equivalent refractive index of GaInAsP at the lasing wavelength of 1.3 μm was 3.50 at 186 K.     

Longitudinal mode behaviors of 1.5 µm range GaInAsP/InP distributed feedback lasers

Longitudinal mode behaviors of asymmetric structure distributed feedback buried heterostructure (DFB-BH) lasers are examined theoretically and experimentally. A 1.5 μm range GaInAsP/InP DFB-BH laser was fabricated by a three-step LPE growth process. We measured the stopband in the spectrum of the DFB laser. It was found that no resonance mode emission occurred in the gain spectrum and its spectrum was asymmetric with respect to the Bragg wavelength. Most of the lasing power concentrated on the DFB mode adjacent to the stop-band which was determined by the Bragg condition. The measured spectrum was explained by the calculated results of the coupled wave theory with external reflectors. The asymmetric spectrum was caused by the relative position of the cleaved facet on the corrugation grating. It was shown that the asymmetric structure DFB laser, which consisted of two end facets with different reflection coefficients, gives a stable single longitudinal mode. There was no mode jump up to 2.3 times threshold. At a modulation depth of 100 percent, the ratio of the highest nonlasing mode intensity to the lasing DFB mode was estimated to be -16.0 dB.     

New 1.6 ?m wavelength GaInAsP/InP buried heterostructure lasers

1.6 ?m wavelength GaInAsP/InP buried heterostructure (b.h.) lasers were fabricated by a new process. The low threshold of 25 mA was obtained for a cavity length of about 300 ?m and stripe width of 3?5 ?m. Room temperature c.w. operation was also obtained with the threshold of 37 mA. Transverse single-mode operation up to more than three times the threshold was obtained.